Electric motor with the rotor connected to the member that is to be rotated

ABSTRACT

In an electric motor having a rotor ( 2 ) and, coaxial therewith, a stator ( 1 ), both contained in a frame ( 3 ), the motor being capable of rotating a member ( 4 ) about an axis of rotation coinciding with the axes of the rotor ( 2 ) and stator ( 1 ), the rotor ( 2 ) is connected in rotation to the member ( 4 ), is hollow and its interior houses a shaft ( 5 ) that supports both it ( 2 ) and the member ( 4 ), and the frame ( 3 ) of the motor is supported by the same shaft ( 5 ) and is connected by an attachment ( 6 ) to a structure that does not participate in the rotation.

The present invention relates to electric motors comprising a rotor and a stator both contained in a frame and using electrical energy to rotate a member connected to them.

Usually (as in a motor-driven rotary pump), the rotor of a motor of this type is integral with a coaxial shaft, to which it transmits the driving torque, and only one end of the shaft projects out of the frame.

However, this type of motor has serious limitations in its modes of use owing to the fact that it has to be mounted in the way hinted at above.

To take one example, in self-propulsion the fact that the shaft driven by the electric motor projects from one side only makes it impossible to mount it directly on the axles of the drive wheels. A transmission system must therefore be used to transmit the rotation of the motor to the axles themselves.

This creates problems in terms of the manufacturing cost, space requirements, the inevitable energy losses and imprecision in the transmission of the drive.

The inventor of the present innovation has provided a solution to this problem by devising a motor which, while comprising the same essential parts (rotor, stator and frame) as electric motors of known type, can be mounted in a very much more advantageous way owing to the particular arrangement of its parts and their connections.

The electric motor according to the invention is characterized in that the rotor is connected in rotation to the said member, is hollow and its interior houses a shaft that acts as a support for the rotor, for the member and for the frame, the frame being connected by means of attachment to a structure that does not participate in the rotation of the said member.

Two preferred embodiments suitable for self-propulsion applications will now be described in more detail by way of example, no limitation or restriction therefore being implied, for which purpose reference will also be made to the accompanying drawings, in which:

FIG. 1 is a view in longitudinal section of a preferred embodiment of the electric motor according to the invention connected to the hub of a wheel in the case in which a part of the rotor is directly fixed to the hub, while FIG. 2 shows the case in which this part is connected to the hub via intermediate speed-reducing gearing, and FIG. 3 shows a longitudinal section through a spindle powered by the electric motor of the invention.

Referring to FIG. 1, it can be seen that the frame 3 is supported by a cylindrical shaft 5 via rolling bearings 10, 11. To keep the frame 3 stationary, it is connected to a rod 6, which may also be provided with joints or damping elastic supports (not shown) and the rod in turn is fixed to a part of the frame of the vehicle (not shown) on which the motor is installed.

A stator 1 is made integral with the frame 3 by systems known to those skilled in the art, and its interior coaxially houses the stator 1, which is also of known type.

Mounted internally and also coaxially with the latter is the rotor 2, which also includes a suitably shaped part 2 c projecting from the frame 3 where it is fixed to the hub 4 of a wheel of the vehicle, which is therefore integral with the rotor 2 in rotation. Lastly, situated coaxially even nearer the centre is a support member 3 a integral with the frame which may also be, as in the case depicted, a part of the frame 3 itself, so that the hub 4 can be clamped following interposition of the abovementioned rolling bears 10, 11 with suitable distance rings 17.

Another rolling bearing 12 (or more than one to reduce the radial thickness from the same load) is inserted lastly between the rotor 2 and the support member 3 a to enable the rotor 2 to be supported without preventing its relative rotation.

As can be seen in FIG. 1, the electric motor mounted on the shaft 5 which supports the member 3 a and the frame 3 is compact and takes up very little space.

The shaft 5 coupled to the electric motor in the embodiments according to the invention functions also as a member that connects and distributes the load between the wheels of one axle, while the rotation is transmitted to the wheels directly by the motors connected to them, it being obvious that one electric motor according to the invention can be fitted for each wheel, that is at both ends of the shaft, resulting in great functionality and ease of assembly and operation.

FIG. 2 meanwhile shows a solution for those cases in which speed reduction is required between the motor and the wheel, that is to say that the wheel is to have a smaller angular velocity than the electric motor connected to it.

The frame 3, stator 1 and rotor 2 are installed as already described in the previous case, but the part 2 c of the rotor 2 projecting from the frame 3 is not now shaped in such a way as to be fixed to the hub 4, but instead includes a first ring gear 8 that meshes with a gear wheel 13 pivoted on a spindle 16 integral with the hub 4, this gearwheel 13 meshing in turn with a second ring gear 9 formed on the frame 3.

Rotation of the said projecting part 2 c of the rotor 2 and of its first ring gear 8 produces rotation of the gear wheel 13, which is connected to the hub 4, and its revolution about the shaft 5 along the second ring gear 9 with a speed of rotation equal to the speed of rotation of the rotor 2 divided by the ratio of the number of teeth of the second ring gear 9 to that of the first ring gear 8. With appropriate numbers of teeth, the speed of rotation of the hub 4 is equal to the said speed of revolution of the gearwheel 13, and is therefore the required amount less than that of the rotor 2.

FIG. 3 meanwhile shows a spindle driven by an electric motor produced in accordance with the invention comprising a rotor 2′ and a stator 1′. This type of application shows very clearly the above-described advantages provided by the invention, such as in particular the small size of the electric motor, and hence of course of the spindle itself, the outer casing of which acts as a frame 3′.

The type of electric motor may be selected on the basis of the preferences of the designers, but the inventor suggests using an asynchronous motor supplied by a high-frequency converter.

It will be obvious that the shape and relative disposition of the parts may be modified by a person skilled in the art depending on particular requirements, but the resulting embodiments, if derivable from the content of the appended claims, will still lie within the scope of protection conferred by the present patent application.

The embodiments described above and illustrated must not therefore be regarded as compulsory or limiting. 

1. Electric motor consisting of a stator and, coaxial therewith, a rotor, both contained in a frame integral with the stator, the motor being capable of rotating a member about an axis of rotation coinciding with the axes of the abovementioned rotor (2, 2′) and stator (1, 1′), which motor is characterized in that the rotor (2, 2′) is connected in rotation to the said member (4), is hollow and its interior houses a shaft (5) that acts as a support for the rotor (2, 2′), for the member (4) and for the frame (3), the frame (3) being connected by means of attachment (6) to a structure that does not participate in the rotation of the said member (4).
 2. Electric motor according to claim 1, in which the member that is to be rotated is a part (4) integral in rotation with a wheel of a vehicle.
 3. Electric motor according to claim 2, in which the rotor (2) is integral with the said part (4) of a wheel of a vehicle and therefore rotates at the same speed as the said wheel.
 4. Electric motor according to claim 2, in which the rotor (2) is connected in rotation to the said part (4) of a wheel of the vehicle by a toothed member (13) pivoted on the said part (4) and meshing with teeth (8, 9) formed on the rotor (2) and on the frame (3), respectively, which rotor (2) rotates at a speed different to that of the wheel.
 5. Electric motor according to claim 3, consisting of: a) a cylindrical shaft (5); b) an outer frame (3) coaxial with the shaft (5), by which it is supported by means of one or more rolling-friction bearings (10, 11); c) a connector rod (6), connecting the frame (3) to a part of the frame of the vehicle; d) a stator (1) keyed internally and coaxially to the frame (3); e) a rotor (2) coaxial with the stator (1) and comprising a part (2 c) that is integral in rotation with a part (4) of a wheel of the vehicle; f) a support member (3 a) interposed coaxially with the cylindrical shaft (5) between the frame and the hub (4) of the wheel of the vehicle; g) one or more rolling bearings (10, 11) interposed between the said shaft (5) and the said support member (3 a); and h) one or more rolling bearings (12) arranged between the support member (3 a) and the rotor (2).
 6. Electric motor according to claim 4, consisting of: a′) a cylindrical shaft (5); b′) an outer frame (3) coaxial with the shaft (5), by which it is supported by means of one or more rolling-friction bearings (10, 11); c′) a connector rod (6), connecting the frame (3) to a part of the frame of the vehicle; d′) a stator (1) keyed internally and coaxially to the frame (3); e′) a rotor (2) coaxial with the stator (1) and having a first ring gear (8) meshing with the teeth of a gear wheel (13) pivoted on a part (4) of a wheel of the vehicle and meshing in turn also with a second ring gear (9) formed on the fixed frame (3); f′) a support member (3 a) interposed coaxially with the shaft (5) between the frame (3) and the hub (4) of the wheel of the vehicle; g′) one or more rolling bearings (10, 11) interposed between the said shaft (5) and the said support member (3 a); and h′) one or more rolling bearings (14, 15) interposed between the rotor (2) and the support member (3 a).
 7. Electric motor according to claim 2 in which the member that is to be rotated is the hub (4) of a wheel of a vehicle.
 8. Electric motor according to claim 1 characterized in that it is of asynchronous type supplied at high frequency. 